1. Field Of The Invention
This invention relates to improved soil release promoting copolymers, method for production thereof and liquid and particulate detergent compositions containing copolymers. More particularly, this invention relates to soil release copolymers having improved hydrolytic stability and shelf life and improved soil release promoting properties, particularly for removal of oily soil from polyester fabric.
2. Description Of The Prior Art
The use of PET-POET soil release promoting polymers is well documented in the patent literature. Representative examples of the patent literature disclosing the use of PET-POET and similar polymers in the treatment of synthetic textile materials is general and in laundry detergent compositions in particular include, among others, U.S. Pat. No. 3,557,039 (and its corresponding British Patent G.B. No. 1,088,984); U.S. Pat. Nos. 3,652,713; 3,723,568; 3,959,230; 3,962,152; 4,125,370; 4,132,680; 4,569,772; and British Patent Specifications G.B. Nos. 1,154,370; 1,317,278; 1,377,092.
U.S. Pat. No. 3,557,039 to McIntyre et al. shows the preparation of such copolymers by the ester interchange and subsequent polymerization of dimethyl terephthalate (DMT) and ethylene glycol (EG) in the presence of a mixed catalyst system of calcium acetate hemihydrate and antimony trioxide. A similar reaction is shown in U.S. Pat. No. 3,959,280 to Hays, this patent further using polyethylene oxide as one reactant in addition to DMT and EG monomers. The PET-POET copolymers of Hays are characterized by a molar ratio of ethylene terephthalate units to polyethylene oxide terephthalate units of from about 25:75 to about 35:65, by the polyethylene oxide of the polyethylene oxide terephthalate having a molecular weight of from about 300 to 700, by the molecular weight of about 25,000 to about 55,000, and by a melting point below 100.degree. C.
U.S. Pat. No. 3,652,713 forms antistatic fibers, films and other shaped articles from compositions in which polyethylene terephthalate is mixed with a polyether-polyester block copolymer such that the polyether segment constitutes from 0.1 to 10.0% by weight based on the total weight of the mixture. The polyether-polyester block copolymer can be prepared by melt-polymerizing (condensation polymerization) polyethylene terephthalate of number average molecular weight of from 1,000 to 2,000 with polyethylene glycol having a number average molecular weight of from 1,000 to 50,000 at a highly reduced pressure and elevated temperature in the presence of antimony trioxide and trimethyl phosphate.
According to G.B. No. 1,317,278 to Ambler, et al. high molecular weight (e.g. spinning grade or film-forming) polyethylene terephthalate is reacted with polyethylene glycol (MW=300 to 20,000) at a temperature in the range of 100.degree. C. to 300.degree. C., preferably at atmospheric pressure in the presence of conventional ester exchange catalyst, for example, antimony oxides, calcium acetate, tetraalkyltitanates and stannous octoate.
U.S. Pat. No. 4,125,370 to Nicol discloses PET-POET soil release promoting random copolymers having an average molecular weight in the range of about 5,000 to about 200,000, with a molar ratio of ethylene terephthalate to polyethylene oxide terephthalate of from about 20:80 to 90:10, the polyethylene oxide linking unit having a molecular weight in the range from about 300 to 10,000. These polymers can be prepared according to the procedure disclosed in the aforementioned patent U.S. Pat. No. 3,959,280 to Hays or by the process described in U.S. Pat. No. 3,479,212 to Robertson et al.
PET-POET soil release promoting polymers are also commercially available, for example, the products Alkaril QCJ and QCF from Alkaril Chemicals, Inc.; Milease T from ICI America; and Zelcon from E.I. duPont de Nemours and Co.
While satisfactory soil release promoting property has been obtained from the commercially available products, as described in the literature, there have been problems with regard to the stability, as well as effectiveness, of these copolymers during storage and under actual use conditions. Thus, U.S. Pat. No. 4,125,370 teaches providing a concentration of certain hardness ions to promote deposition of the soil release polymers on the fabrics being washed and to promote soil release performance. U.S. Pat. No. 4,569,772 teaches that detergent compositions containing PET-POET polymers tend to lose their soil release promoting properties on storage if the compositions contain alkaline builders. The patentees overcome the tendency by comelting the PET-POET copolymer with a water soluble alkali metal polyacrylate and converting the melt to solid particles.
Nevertheless, still further improvements are required for the stability and oily soil release properties of soil release promoting copolymers, especially at low temperatures and under alkaline wash conditions. Furthermore, since the detergent compositions containing soil release promoting polymers are intended primarily for use as a consumer item for sale to individual users for home laundry washing machines it is apparent that cost of additives is a critical factor for the manufacturer and, therefore, any means which can lower production costs without adversely affecting performance or consumer acceptance is of great practical importance.
Generally, those of skill in the art relating to the soil release promoting polymers have concentrated their efforts towards improving product performance by modifying the ratios of PET to POET, or modifying molecular weight of the oxyethylene linking units or by adding still additional stabilizing ingredients, and so on.